package org.daisy.pipeline.common.saxon.impl;
   
   import java.math.BigDecimal;
   
   import static com.xmlcalabash.util.XProcMessageListenerHelper.parseNumber;
   
   import net.sf.saxon.expr.XPathContext;
   import net.sf.saxon.lib.ExtensionFunctionCall;
   import net.sf.saxon.lib.ExtensionFunctionDefinition;
  import net.sf.saxon.om.Sequence;
  import net.sf.saxon.om.StructuredQName;
  import net.sf.saxon.trans.XPathException;
  import net.sf.saxon.value.EmptySequence;
  import net.sf.saxon.value.SequenceType;
  
  import org.daisy.common.messaging.MessageAppender;
  import org.daisy.common.messaging.MessageBuilder;
  
  import org.osgi.service.component.annotations.Component;
  
  @Component(
  	name = "pf:progress",
  	service = { ExtensionFunctionDefinition.class }
  )
  @SuppressWarnings("serial")
  public class ProgressDefinition extends ExtensionFunctionDefinition {
  	
  	private static final StructuredQName funcname = new StructuredQName("pf",
  			"http://www.daisy.org/ns/pipeline/functions", "progress");
  	
  	public StructuredQName getFunctionQName() {
  		return funcname;
  	}
  	
  	public SequenceType[] getArgumentTypes() {
  		return new SequenceType[] {
  			SequenceType.SINGLE_STRING
  		};
  	}
  	
  	public SequenceType getResultType(SequenceType[] suppliedArgumentTypes) {
  		return SequenceType.EMPTY_SEQUENCE;
  	}
  	
  	private static final Sequence VOID = EmptySequence.getInstance();
  	
  	public ExtensionFunctionCall makeCallExpression() {
  		return new ExtensionFunctionCall() {
  			public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
  				try {
  					BigDecimal portion = parseNumber(arguments[0].head().getStringValue());
  					MessageAppender activeBlock = MessageAppender.getActiveBlock();
  					MessageBuilder m = new MessageBuilder().withProgress(portion);
  					// we need an active block otherwise we have no place to send the progress info to
  					if (activeBlock != null)
  						activeBlock.append(m).close();
  					return VOID; }
  				catch (ArithmeticException e) {
  					// probably divided by null, ignore progress info
  					return VOID; }
  				catch (Throwable e) {
  					throw new XPathException("Unexpected error in pf:progress", e); }
  			}
  		};
  	}
  }